The chest X-ray lung cancer screening program of Mayo Lung Project (MLP) yielded mixed results of improved
lung case survival but no improvement in lung cancer mortality. This paper analyzes the smoking patterns of study
participants in order to examine possible behavioral ramifications of periodic lung cancer screening. Using a
longitudinal difference-of-difference model, we compared the smoking behavior, in terms of current smoker status
among all subjects and the intensity of smoking among those continuing smokers, between those who received
periodic lung cancer screening and those who received usual-care. In both arms of this lung cancer screening trial,
there was a sizable decline in cigarette smoking one year after participants received baseline prevalence screening.
There was no significant difference in current smoker status between the intervention group receiving periodic Xray
screening and the control group receiving usual care. While we detect that the continuing smokers in the
intervention group smoked more than their counterparts in the control group, the magnitude of the difference is
not sufficient to explain a substantial difference in lung cancer incidence between the two groups. Our study
shows that periodic lung screening in MLP did not decrease smoking behavior beyond the observed decline
following the initial prevalence screening conducted at baseline for both the intervention and control groups. Our
results also indicate, paradoxically, that participants assigned to the intervention group smoked more cigarettes per
day on average than those in the control group. Lung cancer screening programs need additional cessation
components to sustain the abstinence effect typically observed following initial lung screening.